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Accelerated Rehabilitation Following Anterior Cruciate Ligament Replacement Surgery

Bertram Zarins, MD, William B. Workman, MD, Alex Petruska, PT

Sports Medicine Service, Massachusetts General Hospital


Operative procedures to stabilize knees that have suffered ligamentous injuries have recently undergone dramatic changes. Knees that have sustained multiple ligament tears are often initially treated non-operatively to allow the collateral ligaments to heal. The torn cruciate ligaments are replaced at a later time using arthroscopic techniques.

Concepts regarding post-operative rehabilitation following reconstructive knee surgery have also changed. Instead of immobilization, early motion is encouraged after surgery. An extension of this approach is to use immediate and continuous controlled motion of the knee following anterior cruciate ligament (ACL) replacement surgery. Donald Shelbourne developed the concept of accelerated postoperative rehabilitation. (9,10) This article will describe the postoperative rehabilitation proto-col that is used by the senior author (BZ) at the Massachusetts General Hospital that balances early return to sports participa-tion with adequate time for graft healing.


We use the accelerated rehabilitation protocol when we replace a torn anterior cruciate ligament with a mid-third patellar tendon graft (bone-tendon-bone) using the endoscopic method. Bioabsorbable interference screws are used in the distal femur and proximal tibia, providing graft fixation comparable to metal screws. (18,19) This technique provides immediate stable fixation and allows the knee to be safely moved using the continuous passive motion (CPM) machine after surgery.

We believe the autologous mid-third patellar tendon graft is the best graft for ACL replacement surgery, and we use this graft in all patients in whom we are replacing a torn ACL unless the patient strongly desires an alternative graft. If the patient has had a prior patellar tendon graft that has failed, we use hamstring tendon autograft for revision surgery, if available. We do not use the accelerated rehabilitation program described herein following revision ACL replacement surgery.

Dr. Zarins is Chief, Sports Medicine Service, Massachusetts General Hospital and Associate Clinical Professor of Orthopaedic Surgery, Harvard Medical School

Dr. Workman is a Fellow in Sports Medicine, Harvard Medical School and Massachusetts General Hospital

Alex Petruska
is a Physiotherapist at the Massachusetts General Hospital

Please address correspondence to:
Bertram Zarins, MD
Wang Ambulatory Care Center
Suite 514
Massachusetts General Hospital
Boston, MA 02114


Preoperative protocol

The patient is seen in the office several days before surgery, at which time a preoperative history and physical examination are performed. After the surgeon explains the procedure, the patient watches a video tape detailing the preoperative instructions, surgical procedure, risks, benefits, complications, anesthesia and postoperative course. A physical therapist explains the exercises that will be accomplished during the first week after surgery.

Phase I

Phase I begins immediately after surgery. The doctor applies a continuous passive motion (CPM) machine to the patient’s knee in the operating room, before the patient awakes. The patient remains in the hospital overnight, using the CPM machine continuously. The patient is discharged home the following morning after receiving final instructions on the operation of the CPM machine from a physical therapist. A hinged postoperative brace locked in extension is fitted to be used during ambulation. The patient is allowed to ambulate, full weight bearing, with the postoperative brace in place using crutches.

The patient remains at home for the first seven days after surgery with the knee moving 23 hours a day in the CPM machine. The remaining one-hour per day is designated for necessary activities of daily living and to perform prescribed exercises three times a day (Table 1). Pain medication is pre-scribed as well as elastic stockings and cryotherapy. By the end of the first week the patient should have full knee extension, and 90 degrees of knee flexion.

The CPM machine is set to hyperextend five degrees in which position it pauses for five seconds (extensor pause control on CPM machine). The importance of having the knee go into full extension with each cycle of the CPM is stressed to the patient, as flexion contracture may develop in the absence of vigilant attention to regaining full extension. The speed at which the CPM moves and the amount of flexion reached are not as important

Table I
Goals of Phase I

Phase I Exercise
Protect the reconstruction—avoid falling

1. Heel Prop for passive knee extension
Ensure wound healing

2. Prone Hang for passive knee extension
Attain and maintain full knee extension

3. Quadriceps Setting with emphasis on gaining active control of the “screw home” mechanism
Promote quadriceps muscle strength

4. Heel Slides to gain flexion range of motion
Gain knee flexion to near 90 degrees

5. Sitting Heel Slides to gain flexion range of motion
Decrease knee and leg swelling Avoid blood pooling in the leg veins

6. Ankle pumps

Phase II – one to five weeks after surgery

At the end of the first postoperative week, the patient returns to the office for suture removal and examination by the surgeon. The postoperative brace is shortened, but the hinges remain locked in extension. The patient is instructed Phase II exercises which will be followed for the next four weeks. Full weight bearing is encouraged, and the postoperative brace and crutches may be used as needed for support and comfort. The patient may progressively discontinue using the crutches and brace as soon as the knee feels strong enough to be stable. Most patients discontinue the brace and crutches at approximately two weeks after surgery. Gait is independent (without brace or crutches) between 3 and 5 weeks postoperatively.

Table 2 The patient is instructed to continue all exercises from Phase I during this time. Phase II exercises are added, to be done twice per day (Table 2). The brace is removed when exercising. Stationary cycling with no resistance is recommended on a daily basis for 10 to 15 minutes. If the patient does not have enough knee flexion to complete a full revolution, then he or she pedals back and forth until the knee will flex enough to allow a full cycle.

Phase II exercises include the towel extension stretch with quadriceps setting. The patient, while sitting on the floor or bed, loops a towel around the foot of the operated knee. The patient lets the knee extend fully and flatten against the surface he or she is sitting on. The patient is instructed to pull gently on the towel with both hands until the heel lifts slightly from the surface while keeping the posterior aspect of the knee and calf against the surface. This action helps passively extend the knee to full extension. While holding this position, the patient should actively tighten the quadriceps muscle and hold the contraction for five to ten seconds. The next exercise is the straight leg lift. If the knee has an extensor lag, the patient should not do this exercise.
Goals of Phase II

Phase II Exercise
Protect the reconstruction—avoid falling

1. Towel extension stretch with quadriceps setting
Ensure wound healing

2. Straight leg lift
Maintain full knee extension (straighten knee fully)

3. Standing hamstring curl
Begin quadriceps muscle strengthening

4. Standing toe raises
Attain knee flexion of 90 degrees or more

5. Hip abduction
Decrease knee and leg swelling

6. Mini-squat
Normal gait without crutches 7. Wall slide

The patient should keep trying to do the quadriceps setting exercise until he or she can lift the limb off the bed without letting the knee flex. Additional exercises include standing hamstring curls for active knee flexion and standing toe raises. The wall slide involves supporting the body against a wall and gently squatting to 30-45. Rounding out the Phase II exercises are side-lying hip abduction, mini-squats from 45 to 60 degrees knee flexion, and the wall slide from 45 to 60 degrees knee flexion.

Phase III – five to nine weeks after surgery

Phase III begins at week five and continues through week nine (Table 3). Swimming may begin at this time, using only the standard freestyle kick, also called the flutter kick. This kick allows only vertical scissoring motion of the legs in the sagittal plane, avoiding rotational movements involved in other kicks (e.g. the breaststroke kick). The strokes that are allowed are the freestyle and backstroke. Swimming with a kick board is allowed as long as the flutter kick is used.

If full knee extension has been gained and the knee can be held fully extended during a quadriceps set, the Phase I exer-cises can be discontinued. However, quadriceps-setting exer-cises should continue. Resistance using ankle weights is added for the hamstring curls and straight leg lifts, and the exercise frequency is reduced to 3 times per week. The development of single-leg strength is emphasized at this time. Quadriceps setting exercises should continue daily to ensure that full active knee extension is being maintained. An optional regimen of weight room exercises can be performed during Phase III. For patients who wish to use gym equipment the following exer-cises are considered optional: leg press, quadriceps machine, and hamstring curl machine. The knee extension machine and Stairmaster are to be avoided, as they cause high patellofemoral contact forces (20,21) which can cause, or exacerbate, anterior knee pain following ACL replacement surgery. The patient must refrain from running, jumping, pivoting, and sudden changes in direction. Table 3
Goals of Phase III

Phase III Exercise
1. Protect the reconstruction; avoid falling.
1. Chair squat
2. Maintain full knee extension 2. Single limb concentric eccentric closed chain extensions
3. Attain full knee flexion

3.Single limb wall slides
4. Walk with a normal heel-to gait with no limp.

4. Single limb calf raises
5. Muscle strength and conditioning improvements 5. Hamstring stretch

6. Quadriceps stretch
  7.Calf stretch

Phase IV – from ten weeks following surgery

From the tenth week forward, the patient is in Phase IV of the accelerated ACL rehabilitation protocol. The goals to be attained in Phase IV are to regain full muscle strength, improve cardiovascular conditioning, and perform sports-specific train-ing.

Table 4 The patient is instructed to continue muscle-strengthening exercises from Phases II (Table 2) and III (Table 3) three times per week. To build cardiovascular fitness, the patient is allowed to use any combination of Nordic track, stationary bicycle, rowing machine and swimming. For patients who wish to return to running sports, the patient does an orderly sequence of drills designed to retrain the proprioceptive feed-back loops necessary to provide neuromuscular control of the operated knee, but does not usually begin running until four to six month after surgery (Table 4). The goals of phase IV are to safely recondition the knee, provide a logical sequence of pro-gressive drills for presports conditioning and to provide objec-tive criteria for the patients safe return to sports (Table 5). Sport-specific training and development of functional strength and proprioceptive timing are enhanced and improved as the patient advances throughout the running progression.
Phases of Running Progression

Prerequisites for Running Progression
1. Straight ahead phase

1. Full range of motion
2. Direction change phase

2. Strength at least 80% of the uninjured limb
3. Advanced direction change and impact phase 3. Thigh girth within _ inch of the uninjured limb
4. Sports specific phase

4. Symmetrical quadriceps and hamstring flexibility
  5. Perform and pass functional testing


Table 6

Weeks Postoperative
1. Jogging

2. Slow start-to-slow stop forward and backward running

3. Fast start-to –fast stop forward to backward running

4. Zig-zag running

5. Circle running

6. Figure-of –eight running

7. Carioca running

8. Hop-to-jump progression

9. Run-to-cut progression

10. Sports-specific practice

11. Full return to sports 40
Table 5
Functional Test to Advance to Running Phases Prerequisites for Advancing to Direction Change Phase
1. Hop forward on both legs at least two feet
1. Hop forward on the affected limb for at least 80% of the distance of the unaffected side
2. Hop to either side on both legs at least one foot
2. Hop to either side on the affected limb for 80% of the distance of the unaffected
3. Hop up and down on both feet 10 times symmetrically
3. Hop up and down on the affected limb for 10 times without pain
4. Jog with no limp for 100

A functional brace for sports participation is not routinely prescribed if the knee is stable after surgery. The patient is advised to continue all strength and conditioning drills as part
of a regular fitness and training routine. The patient typically begins unrestricted running at six months after surgery, and unrestricted sports at nine months.


The trend to begin immediate mobilization after ACL replacement surgery with continuous passive motion was first documented in the literature in the early 1980’s (1,7) . Over time, the success with this change in rehabilitation has convinced many orthopaedic surgeons to add early motion in their rehabilitation protocols. (8,15) Often the recovery has been so rapid that athletes have been able to return to play before the graft and/or donor site(s) have healed. In an attempt to push the envelope for return to play, reports of untoward effects such as patella fracture have reached the media. (4,12,14) Experience at both ends of the mobility spectrum has led us to an acceptable timetable for rehabilitation and return to play.

Ample evidence suggests that motion and physiologic loading are essential for proper maintenance and function of articular cartilage. (1) Lengthy immobilization leads to muscle and cartilage atrophy, osteoporosis, and arthrofibrosis. Biomechanical studies suggest that early motion without load bearing will not put the graft or the graft fixation in jeopardy. (16,17)

It is of particular importance to remember that the graft and the patella donor site are probably the weakest at about 3 months. (2,6) This data emphasizes the importance of maintaining motion and continuing strengthening without stressing the graft. Bennyon noted that the anteromedial bundle of the ACL is most stressed towards terminal extension. (4) Because of this, there are some physicians who recommend that patients perform active extension against resistance up to, but not fur-ther than, 40 degrees.

A crucial element of the rehabilitation protocol is regain-ing full extension of the knee. Shelbourne noted that athletes complained of less extremity pain and fatigue after he began emphasizing extension in rehab. (10,11)

Many researchers have noted that open chain kinetic exer-cises markedly increase the shear stresses across the graft, which likely put the graft at risk for stretching or rupture. (3,5,12,13) Closed chain exercises, on the other hand, decrease forces across the patellofemoral joint and all but eliminate shear stress to the tibia, particularly when exercises are performed between 30° and 90° of flexion. (1,7,11,12)

There is evidence to suggest that patients with ACL tears, regardless of whether they have surgery or not, never fully regain quadriceps strength on the affected side. Shelbourne has stated that the best predictor of regaining quadriceps function was a motivated athlete. The most motivated athletes he observed gained 85% to 90% of function at 10 weeks. (9)

Our protocol, unlike the regimens of many other surgeons, minimizes loading of the patellofemoral joint. Patellar tendonitis, anterior knee pain and effusion are common after ACL replacement surgery. We believe that these complications are secondary to some rehabilitation protocols’ reliance on modalities such as stair climbing, lunges and squats for muscle strengthening. Our protocol uses other quadriceps exercises that minimize patellofemoral loading while providing adequate strengthening of the quadriceps muscles. Patients are allowed to discontinue wearing a hinged postoperative knee brace when they have demonstrated good quadriceps strength.

In summary, our rehabilitation protocol following ACL replacement surgery combines early motion with protective strengthening exercises. We have used this protocol for the past five years with all patients who have undergone primary patellar tendon autograft ACL replacement. Since the patients themselves control the amount of flexion during use of the CPM machine, we have encountered very few complications with this accelerated rehabilitation protocol. The goal of this innovative approach is to get the athlete back to playing sports as early and as safely as possible.

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